3 - Offering an owner 50% because you're not sure if the windows that they claim to have just put in are truly the energy efficient kinds, or there isn't some small problem with the foundation that you might not have caught sounds like terrible advice that would surely result in a rejected offer.4 - I've run the numbers fifty times and they make sense for CASH FLOW but the property has been on the market for quite some time and there's a reason for that.

I'd do visual breakdowns summarizing what I've learned, and add enough personality/energy to make it fun.

If you opt for this just check with an electrician first because a heat strip can draw a lot of power 30 - 50 amps.Check out this link to an article on Carrier's website.https://www.carrier.com/residential/en/us/products/heat-pumps/heat-pumps-vs-air-conditioners/Furthermore if you can find a local HVAC engineer or energy calc specialist to run energy calcs for you they can tell you exactly how many tons of heating and cooling you'll need based on the SF of the house, type of windows, type of construction (wall make up, floor make up, roofing etc.), how much insulation is currently installed etc.

The Question: Would it be wiser to invest my time energy and money into rehabbing the units in Ohio FIRST, then moving onto a house hack in LA?

The time, energy and skill required to source, execute and manage deals should not be understated.

I would advise to carefully consider energy costs, zoning for legal TAT, increasing GET tax as well as high cost of on island management. 

Don't waste your time and energy trying to reach them.

When you add up the time and life energy spent, it ending up being a rather big loss.

This is giving me the energy and motivation to look at the syndicates and shop around for a PM.

If you have the time, energy and you understand the process, you can definitely go FSBO.